Enhancing thermal and exergy performance of solar air heaters using tea-dust-based activated carbon nanoparticle coatings on V-corrugated absorbers plate

Abstract

Solar air heaters are widely used for low and medium temperature thermal applications. However, their performance is often constrained by the limited heat absorption capability of conventional absorber coatings. To overcome this limitation, the present study investigates the enhancement of thermal and exergy performance of a V-corrugated solar air heater using activated carbon nanoparticle (ACNP) coatings synthesized from tea dust waste, offering a sustainable and cost effective alternative. ACNP black paint composite coatings with 10 wt%, 20 wt%, and 30 wt% ACNP were prepared and experimentally evaluated under varying mass flow rates and solar intensities. System performance was assessed in terms of thermal efficiency, exergy efficiency, outlet air temperature, and pressure drop, followed by multi response optimization using Response Surface Methodology (RSM). The results revealed that the 20 wt% ACNP coating exhibited superior performance, achieving a maximum thermal efficiency of 77%, exergy efficiency of 4.2%, and an outlet air temperature of 74°C at a mass flow rate of 0.035 kg/s and a solar intensity of 750 W/m². The RSM predicted values showed excellent agreement with experimental data (R² > 0.98), confirming model reliability. The findings demonstrate that tea waste derived ACNP coatings significantly enhance heat absorption and energy utilization while maintaining acceptable pressure drop. The novelty of this work lies in integrating agro waste derived nanomaterials with thermo exergetic optimization for sustainable solar air heater enhancement.